Conventional centrifugal pumps typically use a rotating shaft to transmit power from an external motor to the pump impeller. Where this shaft passes through the pump casing, a mechanical seal is required to contain the pumped fluid.

The mechanical seal therefore represents a dynamic sealing interface and a potential wear and leakage point.

This can become particularly challenging in cryogenic pump applications, where seals and surrounding components are subjected to extremely low temperatures, thermal cycling and dimensional changes caused by thermal contraction.

A sealless pump removes this dynamic shaft sealing interface.

In a canned motor pump configuration, the pump and electric motor are integrated into a single unit, allowing torque to be transmitted to the impeller without an external rotating shaft passing through the pressure boundary.

For applications such as LNG transfer, liquefied gas handling and other critical cryogenic services, these characteristics can make sealless technology particularly attractive compared with conventional mechanically sealed pump designs.

Cryogenic fluid containment is a critical consideration when handling liquefied gases that may be flammable, volatile, oxidizing or otherwise hazardous.

Liquefied natural gas, for example, combines extremely low operating temperature with flammability and rapid vaporization if released into warmer surroundings. Other cryogenic fluids present different hazards and therefore require application-specific containment and safety considerations.

A sealless cryogenic pump eliminates the dynamic mechanical seal and its associated external leakage path.

The integrated motor-and-pump architecture provides a hermetically contained pumping configuration designed to keep the process fluid within the pump pressure boundary.

This is particularly relevant for applications involving:

• LNG and liquid methane,
• liquid nitrogen and other industrial gases,
• volatile liquefied gases,
• flammable cryogenic fluids,
• hazardous low-temperature process fluids,
• critical cryogenic transfer applications.

For plant operators, EPC contractors and process engineers, enhanced containment can also contribute to broader operational objectives such as reducing fugitive emissions, limiting product losses and minimizing maintenance interventions associated with shaft sealing systems.

However, sealless design does not eliminate the need to evaluate the complete pumping system. Materials compatibility, connections, piping, instrumentation, operating conditions and project-specific safety requirements must all be considered when engineering a cryogenic installation.

OPTIMEX has developed a specific wet-stator motor design for cryogenic pumping applications.

Unlike conventional dry-stator canned motor designs where a containment shell separates the stator from the pumped fluid, the OPTIMEX wet-stator configuration allows the rotor and stator to operate immersed in the pumped cryogenic liquid.

The electrical components are protected by a specialized encapsulation system compatible with the operating environment, while the cryogenic liquid participates directly in motor cooling.

This architecture provides several advantages for demanding low-temperature applications:

• no conventional mechanical shaft seal,
• direct motor cooling by the pumped cryogenic liquid,
• compact integrated pump-and-motor design,
• fully submerged pump configurations,
• suitability for installation directly inside certain cryogenic storage tanks,
• reduced external leakage paths,
• adaptation to demanding low-NPSH cryogenic applications,

For submerged installations, the complete pump and motor assembly can be positioned directly in the cryogenic liquid, providing an in-tank cryogenic pumping solution particularly relevant to certain storage and transfer applications.

The wet-stator architecture must nevertheless be engineered according to the specific fluid and operating conditions. Temperature, pressure, fluid properties, electrical requirements, materials compatibility, thermal balance and hydraulic performance all need to be evaluated for each cryogenic pump application.

By combining sealless pump technology with wet-stator motor engineering, OPTIMEX can develop specialized cryogenic pumping solutions for applications where fluid containment, low-temperature operation and custom engineering are key project requirements.

Every custom cryogenic pump project begins with a detailed analysis of the process conditions and required operating envelope.

Cryogenic pump engineering must account for the interaction between hydraulic performance, thermodynamic behavior, mechanical design, materials and motor technology.

Key project data evaluated during the engineering phase can include:

• pumped fluid and fluid composition;
• minimum, normal and maximum operating temperature;
• minimum, normal and maximum flow rate;
• suction and discharge pressure;
• required Total Dynamic Head;
• fluid vapor pressure;
• available NPSH;
• minimum and maximum tank liquid levels;
• continuous, intermittent or variable operating duty;
• installation and space constraints;
• materials compatibility;
• electrical supply and motor requirements;
• hazardous area requirements where applicable;
• instrumentation and monitoring requirements.

For cryogenic fluids, hydraulic sizing must also be considered together with thermal behavior.

Heat introduced by the motor, hydraulic losses or the surrounding environment can affect the condition of a liquefied gas and potentially promote vaporization. OPTIMEX therefore considers thermal balance as part of the cryogenic pump engineering process to verify that the proposed design is compatible with the required operating conditions.

Where available NPSH is limited, the hydraulic configuration can also be evaluated to address demanding suction conditions. Depending on the application, solutions can include submersible pump installation, in-tank configurations or an inducer designed to reduce NPSHr.

This application-specific engineering approach enables the cryogenic pump to be designed around the complete system requirements, rather than treating flow rate or discharge pressure as isolated selection criteria.

Control of the complete pump development process is particularly important for custom cryogenic pumping equipment, where hydraulic, mechanical, electrical and thermal performance are closely interconnected.

OPTIMEX manages key stages of its pump development and production process in-house, from engineering and design through manufacturing, assembly and testing.

Its capabilities include:

• hydraulic and mechanical engineering,
• pump and motor design,
• component manufacturing and machining,
• motor winding,
• electrical component encapsulation,
• rotor balancing,
• pump and motor assembly,
• performance testing,
• final inspection and quality control,

This integrated manufacturing approach allows the different elements of a sealless cryogenic pump to be developed as a complete system.

For OPTIMEX wet-stator cryogenic technology, the relationship between the hydraulic section, motor, encapsulated electrical components and pumped fluid is particularly important because the motor operates in direct contact with the cryogenic liquid.

Keeping core engineering and manufacturing capabilities under direct control also facilitates the development of custom pump configurations when standard dimensions, hydraulics, materials or installation arrangements cannot meet the project requirements.

Testing forms an essential part of this process.

Depending on the pump and project specification, testing can be used to verify parameters such as hydraulic performance, flow rate, head, electrical behavior, vibration, leak tightness and overall operating performance before delivery.

Project-specific inspection, testing and documentation requirements can also be defined according to the end user’s specifications and applicable contractual requirements.

A custom cryogenic pump becomes particularly relevant when the application falls outside the operating envelope of conventional catalog equipment.

OPTIMEX can adapt the hydraulics, motor, materials, pump orientation and installation configuration according to the requirements of the application.

This engineering capability is particularly relevant for critical cryogenic applications involving LNG storage and transfer, industrial gases, Air Separation Units, cryogenic process plants and specialized low-temperature installations.

For projects involving emerging or particularly demanding fluids and markets — including liquid hydrogen, LOX, aerospace or space-related cryogenic applications — the required pump configuration and suitability must be specifically evaluated and validated according to the fluid, operating envelope, applicable standards and project requirements.

The objective is not simply to supply a cryogenic pump, but to provide an engineered pumping solution matched to the process conditions and installation constraints of the project.

For EPC contractors, process engineers, equipment specifiers and industrial end users, this custom approach provides a direct path from the cryogenic pump specification and duty point to engineering, manufacturing, testing and project support.